One of the most important lessons to be learned from Flixborough,
perhaps the most important, was ignored in the official report and in most
of the other papers which have appeared on the subject: If the inventory
had been smaller the leak would have been less. What you don’t have, can’t
leak. In fact, it was Flixborough that made chemical engineers realise that
it might be possible to reduce inventories. Before Flixborough most
companies designed plants and accepted whatever inventory was called for
by the design. Many companies still do so. However, an increasing number
now realise that if we set out to reduce inventories it is often possible to
do so and that the resulting plants are cheaper as well as safer. They are
cheaper because less added-on protective equipment is needed, and has
to be tested and maintained, and because a smaller inventory means
smaller, and therefore cheaper, equipment. My book Process Plants: A
Handbook for Inherently Safer Design5
and other publications6 give many
examples of what has been and might be done. Such plants are said to be
inherently safer to distinguish them from conventional or extrinsically safe
plants where the safety is obtained by adding on safety features.